19  Unit 4: Climate Change - Unit Closing

How do natural factors contribute to changes in Earth’s temperature? Why are scientists so sure humans are causing climate change today?

Author

Earth & Space Science

HS-ESS3-1 HS-ESS3-5

20 Returning to the Anchor Phenomenon

20.1 🌍 Our Anchor Phenomenon Revisited

Earth’s temperature is rising, reversing the cooling trend that occurred over the past 2,000 years, putting millions of people in harm’s way, yet the public is not convinced of the risks.

20.1.1 You Can Now Explain:

✅ How natural factors have contributed to climate change in the past
✅ Why those natural factors cannot explain current warming
✅ What evidence convinces 99.9% of climate scientists that humans are the cause
✅ Why this matters for human populations

21 Synthesizing Your Learning

21.1 The Complete Climate Story

21.1.1 Interactive Evidence Summary Dashboard

21.2 Why Scientists Are Certain: The Complete Picture

21.2.1 The Scientific Consensus Explained

Multiple independent lines of evidence ALL point to the same conclusion:

Evidence Type What It Shows Natural Explanation?
Ice cores (CO₂) CO₂ at 800,000-year high ❌ No natural source
Carbon isotopes Fossil fuel fingerprint ❌ Proves human origin
Warming pattern Matches greenhouse effect ❌ Rules out solar
Timing Matches industrialization ❌ Rules out natural cycles
Rate of change 100x faster than natural ❌ Rules out all natural causes
Climate models Predictions match observations ✅ Only works with human emissions

This is why 99.9% of climate scientists agree: The evidence is overwhelming and consistent across dozens of independent data sources and methods. There is no alternative explanation that fits all the evidence.

21.3 Interactive: Build Your Argument

22 Performance Task

22.1 📋 Your Mission: Climate Communication

22.1.1 The Challenge:

Create a communication piece for someone in your community that:

  1. Explains why scientists are certain that humans are causing climate change
  2. Uses evidence from multiple sources we’ve studied
  3. Addresses at least one common misconception
  4. Predicts how climate factors will be affected
  5. Explains why it matters (human impacts)

22.1.2 Format Options:

Choose ONE of the following:

  • 📝 Written article or blog post (800-1200 words)
  • 📊 Infographic or poster (visual with explanatory text)
  • 🎬 Video presentation (3-5 minutes)
  • 📱 Social media campaign (series of 5-7 posts with graphics)
  • 🎙️ Podcast episode (5-8 minutes)
  • ✉️ Letter to a local official (with supporting evidence)
  • 🎭 Presentation for a community group (with slides)

22.2 Performance Task Rubric

Criteria Exemplary (4) Proficient (3) Developing (2) Beginning (1)
Scientific Accuracy
(HS-ESS3-5)
All claims are scientifically accurate with specific data cited from unit materials Claims are accurate with some specific data cited Some claims are accurate but lack supporting data Contains scientific inaccuracies or unsupported claims
Evidence Usage
(HS-ESS3-5)
Uses 4+ types of evidence (CO₂, temperature, attribution, impacts) effectively integrated Uses 3 types of evidence effectively Uses 2 types of evidence Uses 1 or no types of evidence
Addresses Natural Factors
(HS-ESS2-4)
Thoroughly explains why Milankovitch cycles, solar changes, and volcanic activity cannot explain current warming Explains why most natural factors cannot explain current warming Mentions natural factors but explanation is incomplete Does not address natural factors
Human Impacts
(HS-ESS3-1)
Clearly explains current AND future impacts with specific examples and data Explains current and future impacts with some examples Mentions impacts but lacks specific examples Does not adequately address human impacts
Addresses Misconceptions Effectively addresses misconception using acknowledge-counter-evidence-conclude structure Addresses misconception with evidence Mentions misconception but response is weak Does not address any misconceptions
Communication Quality Clear, engaging, well-organized, and perfectly appropriate for intended audience Clear and mostly appropriate for audience Somewhat clear but may not suit audience well Unclear, disorganized, or inappropriate for audience

22.3 📝 Performance Task Planning Sheet

Step 1: Define Your Audience

Who are you trying to reach? (Be specific!)

Audience Option Their Likely Prior Knowledge Their Likely Concerns
Family member (skeptical) May have heard climate myths Cost of action, political concerns
Younger sibling/cousin Basic science knowledge Future impacts on their life
Local business owner Practical focus Economic impacts
School board member Education-focused How to teach this topic
City council member Policy-focused Local impacts, what they can do

My chosen audience: _______________________________________________

Step 2: Identify Their Questions/Concerns

What might they already believe or wonder about climate change?




Step 3: Select Your Evidence

Evidence Type Specific Data Point from Unit How I’ll Present It
CO₂ evidence
Temperature evidence
Attribution evidence
Impact evidence
Historical evidence (AMOC/Younger Dryas)

Step 4: Choose a Misconception to Address

Which misconception is your audience most likely to hold?

How will you address it?

  • Acknowledge: _______________________________________________
  • Counter: _______________________________________________
  • Evidence: _______________________________________________
  • Conclude: _______________________________________________

Step 5: Plan Your Call to Action

What do you want your audience to understand or do after engaging with your piece?


Step 6: Choose Your Format

Format selected: _______________________________________________

Why this format works for your audience: _______________________________________________

23 Unit Summary

23.0.1 💡 Complete Unit Key Ideas

From Earth-Sun Dynamics (HS-ESS2-4): - Milankovitch cycles (eccentricity, obliquity, precession) drive glacial-interglacial cycles - These cycles operate on 23,000 to 100,000 year timescales - Summer radiation at 65°N controls ice sheet growth/retreat - Current orbital configuration predicts gradual COOLING — yet Earth is warming

From Climate Feedbacks (HS-ESS2-2, HS-ESS2-4, HS-ESS2-6): - The greenhouse effect traps heat via absorption of infrared radiation - CO₂ is now 422 ppm (50% higher than any point in 800,000 years) - Ice-albedo feedback amplifies warming (positive feedback loop) - Arctic warms 4x faster due to ice-albedo feedback - Multiple feedback loops (ice-albedo, water vapor, permafrost) accelerate change

From The Past and The Future (HS-ESS2-4, HS-ESS3-1, HS-ESS3-5): - AMOC is driven by cold, salty water sinking in the North Atlantic - Freshwater from melting ice weakens AMOC - The Younger Dryas (~12,900 years ago) shows AMOC can shut down rapidly - AMOC shutdown caused ~10°C cooling in decades, devastating human populations - AMOC is currently showing signs of weakening - Millions are already affected; hundreds of millions at future risk

The Bottom Line: - ✅ Climate change is definitely caused by human activity - ✅ Natural factors cannot explain current warming - ✅ Increasing temperatures will affect sea ice, sea level, weather patterns, food, and water - ✅ Climate change will affect billions through disasters, displacement, and resource shortages - ✅ Understanding the past helps us prepare for and potentially prevent future disasters

24 Final Reflection

24.0.1 🤔 Unit Reflection Questions

Looking Back at Your Learning:

  1. At the beginning of this unit, what did you think caused climate change? How has your understanding evolved?

  2. What was the most surprising or compelling piece of evidence you encountered?

  3. Which concept was most challenging to understand? How did you work through it?

Connecting the Concepts:

  1. How do Milankovitch cycles, the greenhouse effect, and AMOC all connect in the climate system?

  2. Why is the Younger Dryas relevant to understanding potential future climate risks?

  3. How does understanding natural climate change actually STRENGTHEN the case that current warming is human-caused?

Looking Forward:

  1. How might climate change affect your community in your lifetime?

  2. What role can individuals, communities, and governments play in addressing climate change?

  3. How will you use what you’ve learned to communicate about climate change with others?

Returning to the Anchor Phenomenon:

  1. Can you now fully explain why 99.9% of climate scientists are certain about human-caused climate change?

  2. Why do you think there’s a gap between scientific consensus and public perception?

  3. What responsibility do scientifically-informed citizens have in bridging that gap?

25 Interactive Unit Review

25.1 Comprehensive Topic Review


25.2 📝 Unit Closing Assessment

25.2.1 Part A: Multiple Choice

Question 1: What is the main reason scientists are confident that current warming is NOT caused by changes in Earth’s orbit (Milankovitch cycles)? - A) Earth’s orbit hasn’t changed - B) Current orbital configuration predicts cooling, not warming - C) Milankovitch cycles were disproven - D) Orbital changes only affect the Southern Hemisphere

Question 2: Current atmospheric CO₂ levels are approximately: - A) 280 ppm (same as pre-industrial) - B) 350 ppm - C) 422 ppm - D) 600 ppm

Question 3: How do scientists know that the increased CO₂ comes from fossil fuels? - A) They can see smoke from factories - B) Carbon isotope ratios show a fossil fuel fingerprint - C) They counted all the power plants in the world - D) It’s an educated guess

Question 4: Why is the Arctic warming almost 4 times faster than the global average? - A) The Arctic is closer to the Sun - B) Ice-albedo feedback amplifies warming there - C) There are more volcanoes in the Arctic - D) The Arctic has more CO₂

Question 5: What caused the Younger Dryas rapid cooling event ~12,900 years ago? - A) A massive volcanic eruption - B) Decreased solar output - C) Freshwater from melting ice shutting down AMOC - D) An asteroid impact

Question 6: How long did the Younger Dryas cold period last? - A) About 100 years - B) About 1,200 years - C) About 10,000 years - D) About 100,000 years

Question 7: Which evidence rules out solar changes as the cause of current warming? - A) The Sun doesn’t affect Earth’s climate - B) Solar output has been flat/declining since 1980, and the stratosphere is cooling - C) Solar output has increased dramatically - D) Scientists haven’t studied solar output

Question 8: What percentage of climate scientists agree that humans are causing current climate change? - A) About 50% - B) About 75% - C) About 90% - D) About 99.9%

Question 9: If AMOC significantly weakens, what would likely happen to Northwestern Europe? - A) It would warm dramatically - B) It would experience significant cooling despite global warming - C) Nothing would change - D) It would experience more earthquakes

Question 10: Why is the rate of current warming important evidence for human causation? - A) Fast warming is always natural - B) Current warming is 100x faster than natural changes, ruling out natural causes - C) Warming rate doesn’t matter - D) Natural warming is always faster than human-caused warming

Question 11: What drives the sinking of water that powers AMOC? - A) Wind pushing water down - B) Cold, salty water being denser than warm, fresh water - C) The Moon’s gravitational pull - D) Underwater volcanoes

Question 12: Which statement best explains why understanding past climate change strengthens the case for human causation of current warming? - A) Past climate was always stable - B) By understanding natural causes, scientists can show they don’t explain current warming - C) Past climate changes prove current warming is natural too - D) Past climate is irrelevant to understanding current climate

25.2.2 Part B: Short Answer

Question 13: Explain why the fact that Earth was cooling for 2,000 years before recent warming is important evidence for human causation. (3-4 sentences)

Question 14: Describe the ice-albedo feedback loop and explain why it causes the Arctic to warm faster than the rest of the planet. (4-5 sentences)

Question 15: A classmate says “The climate has always changed, so current warming is natural.” Using evidence from this unit, construct a response that addresses this claim. (5-6 sentences)


25.2.3 Answer Key

Multiple Choice: 1-B, 2-C, 3-B, 4-B, 5-C, 6-B, 7-B, 8-D, 9-B, 10-B, 11-B, 12-B

Short Answer Rubric:

Question 13 (4 points): - States that Milankovitch cycles predicted continued cooling (1 pt) - Explains that warming reversed this natural trend (1 pt)
- Concludes this rules out natural orbital causes (1 pt) - Uses specific timeframes or data (1 pt)

Question 14 (5 points): - Correctly defines albedo (1 pt) - Explains ice has high albedo, ocean has low albedo (1 pt) - Describes the feedback loop mechanism (1 pt) - Explains why this amplifies warming in the Arctic specifically (1 pt) - Uses specific numbers (e.g., 60% vs 6% albedo) (1 pt)

Question 15 (6 points): - Acknowledges that climate has changed naturally (1 pt) - Explains natural causes (Milankovitch cycles) and their timescales (1 pt) - States current warming is 100x faster than natural (1 pt) - Provides additional evidence (CO₂ levels, isotopes, solar data) (1 pt) - Explains why natural factors are ruled out (1 pt) - Concludes that only human emissions explain observations (1 pt)


25.3 Congratulations! 🎉

You have completed Unit 4: Climate Change. You now have the scientific knowledge to:

  • ✅ Explain how natural factors have influenced Earth’s climate over hundreds of thousands of years
  • ✅ Describe why those same natural factors cannot explain current warming
  • ✅ Present multiple lines of evidence that demonstrate human causation
  • ✅ Explain climate feedback mechanisms and why they matter
  • ✅ Connect past climate events to potential future risks
  • ✅ Communicate effectively about climate science to others

Your voice matters. Use your knowledge to help bridge the gap between scientific consensus and public understanding. The future depends on informed citizens who can evaluate evidence and make decisions based on science.